Armour

ABSTRACT

A bullet-resistant armour element for use as a tessellation in a flexible armour matrix has a hard main body and a facing over said main body, such as layer of polymeric or polymer matrix composite material, wherein the facing has an acoustic impedance which is substantially lower than the acoustic impedance of the main body. Groups aid elements tessellate to form an aperture between the adjacent elements, and a cover element is arranged to cover said aperture. Limit stops restrict the degree of articulation between the adjacent elements. The elements include a deflector for deflecting bullet splash and traps for collecting bullet splash.

The present invention relates to armour, more particularly, but notexclusively, to armour that is intended to be worn by a user, forexample flexible armour systems and bullet-resistant armour.

Flexible body armour has been in existence for many hundreds of years.One known form of flexible body armour is similar to the protective coatof an armadillo, wherein rows of overlapping armour plates are arrangedin such a way that relative movement between adjacent rows is possible,without exposing a significant gap between the rows.

Typically, conventional systems require a significant degree of overlapbetween the adjacent rows. This, of course, increases the weight of thearmour. In modem times, the weight and or bulk of the material requiredto provide reliable armour performance against armour-piercing bulletsand the like makes the use of such overlapping systems impractical forpersonal armour systems requiring effective bullet resistance.

An object of the invention is to provide armour elements which are moresuited to modern day combat requirements, in terms of flexibility and/orbullet resistance.

According to a first aspect of the invention, there is provided anarmour element for use as a tessellation in a flexible armour matrix.

The armour element is preferably polygonal in plan view, more preferablyin the form of an octagon. The polygonal element is preferablyconfigured so that, in tessellation with other elements of the same kindand configuration, an aperture is formed between said elements.

The armour element preferably comprises a hard element, more preferablya hard element suitable to provide bullet-resistance. That is to say,the armour element is preferably configured for use in bullet-resistantarmour systems, as opposed to armour systems configured for resistingknife-attack, for example. The skilled person will therefore be able toconstrue the term ‘hard element’ accordingly.

The skilled person would be readily able to identify materialsexhibiting hardness and/or acoustic impedance properties suitable foruse in bullet-resistant armour systems, and so such materials or methodsfor configuring such materials to promote such properties are notdescribed herein in detail. Hardness and acoustic impedance areintrinsic properties of certain materials and those with knowledge willbe able to develop and/or select from existing commercial materialsthose which are suitable for application in a bullet-resistant armoursystem.

In preferred embodiments, the hard element is made of a ceramicmaterial, and may be a ceramic-ceramic composite or ceramic-metalcomposite.

In preferred embodiments, the hard element has a hardness and/oracoustic impedance suitable to efficiently defeat modern day armourpiercing bullets such as tungsten carbide or steel cored bullets, e.g.configured with a hardness of at least 15 GPa (Hv_(0.5) 1500 Kg mm⁻²)and/or with an acoustic impedance of at least 35 MRayl. This may involvea ceramic or ceramic composite, and examples of materials suitable foruse in providing a hard element with such hardness and/or acousticimpedance properties include aluminium oxide, silicon carbide and boroncarbide.

In other embodiments, the armour may be specifically configured fordealing with lead or mild steel cored ball round and/or fragmentationfrom explosive ordnance devices (i.e. so as to be generally unsuitablefor defeating tungsten carbide or steel cored bullets), in which casethe hard element may be configured with a hardness in the region of 3GPa and/or with an acoustic impedance in the range of 10 MRayl. Thematerials for use in providing such hardness and/or acoustic impedanceproperties include silicates, porcelain glasses, glass ceramics, metalor combinations thereof.

Other materials (e.g. metals, ceramics and metal matrix composites) maybe applicable for achieving specific hardness/acoustic impedance valuesfor other specific armour applications.

The acoustic impedance of the hard element is preferably suitable toproduce a shock wave in a bullet core sufficient to fragment the bullet,upon impact with the armour element. The effect is to disperse kineticenergy from the bullet, thereby reducing the penetrative capability ofthe bullet.

The armour element preferably includes a facing over the hard element,such as layer of polymeric or polymer matrix composite material. Thefacing may be a single component specific to a single armour element, ormay take the form of a continuous component configured to extend acrossan array of two or more armour elements. In the latter instance, thefacing is preferably of elastomeric material, suitable to permitrelative movement between the armour elements in the array.

The facing is preferably configured for promoting dynamicpre-compression of the upper surface of the hard element, suitable tocause a temporary increase in hardness of the material, upon impact froma bullet. This may be suitable to partially defeat armour piercingbullets impacting with the face of the armour element, an effectcommonly referred to as ‘interface defeat’. This delays or restrictspenetration to the hard element and increases the performance of thearmour element.

To provide the above effect, the facing preferably has an acousticimpedance which is substantially lower than the acoustic impedance ofthe hard element, e.g. less than 25% of the acoustic impedance of thehard element. The purpose of the facing is to acoustically decouple theeffect of the impact from the bullet, to reduce the effect of shockwaves generated by the impact from passing through the hard element andcausing premature failure of the armour element. In the case of ceramicand ceramic composite materials, the crystal lattice of the hard elementexhibits little or no plastic behaviour and so the pressure of theimpact will cause the lattice structure to deform, generating alocalised hardening of lattice structure. However, in the absence of anacoustic decoupling facing, the impact may simultaneously generateshockwaves capable of fracturing the lattice structure, which, inaddition to the pressure from the impact, may cause premature failure ofthe armour element.

The hard element preferably comprises the main body of the armourelement, and is preferably mounted on a base forming a back plate forthe armour element. The base is preferably in the form of a layer ofmetal material, e.g. titanium, steel or aluminium. In other embodiments,the base is a fibre reinforced composite (e.g. using glass or carbonfibre), or is made of rubber or plastic.

The base is preferably cupped or otherwise configured to provide alateral constraint for the sides of the hard element.

According to a further aspect of the invention, there is provided abullet resistant armour element, comprising a main body mounted on abase, wherein the main body has a hardness and/or acoustic impedancesuitable to efficiently defeat modem day armour piercing bullets such astungsten carbide or steel cored bullets, e.g. configured with a hardnessof at least 15 GPa (Hv_(0.5) 1500 Kg mm⁻²) and/or with an acousticimpedance of at least 35 MRayl.

This may involve a ceramic or ceramic composite, and examples ofmaterials suitable for use in providing a main body with such hardnessand/or acoustic impedance properties include aluminium oxide, siliconcarbide and boron carbide.

The acoustic impedance of the main body is preferably suitable toproduce a shock wave in a bullet core sufficient to fragment the bullet,upon impact with the armour element. The effect is to disperse kineticenergy from the bullet, thereby reducing the penetrative capability ofthe bullet.

The armour element preferably includes a facing over the main body, suchas layer of polymeric or polymer matrix composite material. The facingmay be a single component specific to a single armour element, or maytake the form of a continuous component configured to extend across anarray of two or more armour elements. In the latter instance, the facingis preferably of elastomeric material, suitable to permit relativemovement between the armour elements in the array.

The facing is preferably configured for promoting dynamicpre-compression of the upper surface of the main body of the armourelement, to delay or restrict penetration to the main body and increasethe performance of the armour element. This is discussed in more detailwith reference to the above aspect of the invention. Accordingly, thefacing preferably has an acoustic impedance which is substantially lowerthan the acoustic impedance of the main body, e.g. less than the of 25%of the acoustic impedance of the main body.

The main body is preferably mounted on a base forming a back plate forthe armour element. The base is preferably in the form of a layer ofmetal material, e.g. titanium, steel or aluminium. In other embodiments,the base is a fibre reinforced composite (e.g. using glass or carbonfibre), or is made of rubber or plastic.

The base is preferably cupped or otherwise configured to provide alateral constraint for the sides of the main body.

The armour element is preferably polygonal in plan view, more preferablyin the form of an octagon. The polygonal element is preferablyconfigured so that, in tessellation with other elements of the same kindand configuration, an aperture is formed between said elements.

The main body is preferably of ceramic material. In preferredembodiments, the main body may be of ceramic-ceramic composite orceramic-metal composite.

In addition, the armour element may incorporate one or more of thepreferred or essential features of the armour elements referred to inany of the other aspects of the invention mentioned herein.

According to another aspect of the invention, there is provided aflexible armour system comprising an array of armour elements intessellation to form an aperture therebetween, and a cover elementarranged to cover the aperture between the elements.

The armour system preferably includes a backing layer suitable forcollecting sporation or debris behind the array of armour elements. Thisrenders the armour system suitable for use as a stand alone body armour,which obviates the need for a ballistic vest. The backing layer maycomprise an array of overlapping elements, each coupled to a respectivecover element, e.g. via a shaft passing through the array of armourelements, in which the backing elements preferably comprise a hardfibrous composite armour material.

Armour elements in the array may be of the kind referred to in any ofthe other aspects of the invention mentioned herein.

According to yet another aspect of the invention, there is provided anarmour element having a hard main body and a facing for the main body,wherein the facing has an acoustic impedance which is substantiallylower than the acoustic impedance of the main body, e.g. less than theof 25% of the acoustic impedance of the main body.

In addition, the armour element may incorporate one or more of thepreferred or essential features of the armour elements referred to inany of the other aspects of the invention mentioned herein.

According to another aspect of the invention, there is provided anarmour element having a hard main body and an acoustic decouplingfacing. The facing is preferably configured a) to permit pre-compressionof the main body upon impact from a bullet and b) to reduce thetransmission of shock waves to the main body as a result of the impact.

This is particularly useful in defeating the effects of armour piercingbullets, by enabling the main body to pre-compress and strengthen uponimpact, an effect known as ‘interface defeat’, thus delaying orrestricting the penetration to the main body and increasing armourperformance, as well as by reducing the magnitude of potentiallydestructive shock waves travelling through the main body as a result ofthe impact.

In addition, the armour element may incorporate one or more of thepreferred or essential features of the armour elements referred to inany of the other aspects of the invention mentioned herein.

According to still a further aspect of the invention, there is providedan armour element having a hard main body mounted on a base, wherein themain body is located on the base in such a way as to protect the mainbody against shock waves from the interface between the main body andthe base member.

The main body is preferably joined to the base using an adhesive havingrubber properties or may be partially acoustically coupled to the baseusing an adhesive or cement incorporating a compound of polymer loadedwith a high impedance material, such as a ceramic or dense metal powder.In other embodiments, the base may be of metal and the main body can bebrazed or diffusion bonded thereto. The main body may have a rear faceof porous nature, whereby the base metal may be partially infused to themain body to make an interpenetrating metal ceramic composite structure.

In addition, the armour element may incorporate one or more of thepreferred or essential features of the armour elements referred to inany of the other aspects of the invention mentioned herein.

According to a yet further aspect of the invention, there is provided aflexible armour system including a group of armour elements arranged ina tessellated array, wherein each element in the array is movablerelative to an adjacent element in the array, and wherein the arraydefines an aperture between the group of elements, the amour systemfurther including a cover element arranged to cover the aperture in thearray, wherein the cover element is movable relative to each element inthe array.

The cover element preferably has a stem which extends through theaperture between the tessellated armour elements. A back stop ispreferably connected to the stem to limit movement of the cover elementrelative to the array. The back stop preferably includes a backingelement, the backing elements in the system being configured to overlapwith one another so as to form a backing layer suitable for collectingsporation or debris behind the array of armour elements. The backingelements preferably comprise a hard fibrous composite armour material.

The cover element is preferably configured to cover a proportion of thejoint between adjacent pairs of the tessellated elements when the uppersurfaces of the elements are in register with one another. In apreferred embodiment, the cover element is configured to coverapproximately 50 percent of each joint.

The armour system may include a plurality of said groups, each grouphaving its own cover element.

The or each cover element preferably has a cap which rests in abutmentwith the upper surfaces of the elements in the array. The cap ispreferably dome-shaped, for deflecting armour piercing bullets.

A nested joint is preferably provided between adjacent elements in theor each array. The nested joint is preferably configured to permitarticulation between adjacent elements in the array. Preferredembodiments include limit stops between adjacent elements in the array,to restrict the degree of articulation between the adjacent elements.

The nested joint is preferably defined by a convex formation on oneelement and a complementary concave formation on the other element.

In a preferred embodiment, adjacent elements in the or each array arearranged for articulation relative to one another, and wherein thedegree of articulation between the adjacent elements is restricted toprevent or limit the risk of significant gaps from being generatedbetween the adjacent elements. A rolling joint is preferably providedbetween the adjacent elements in the array, consisting of a concave sideon one of the elements which is nested with a convex side on the otherof said elements, and wherein the concave side incorporates an earhaving a recess, and the convex side has a rib or projection configuredto be received in the recess of an adjacent element, wherein the recessacts as a limit stop for the projection, so as to limit the degree ofrolling at each joint.

The ear preferably acts as a deflector for deflecting bullet splash. Therecess preferably acts as a trap for collecting bullet splash.

In preferred embodiments, the ear is configured to extend beneath anadjacent element in the array. The ear preferably has a curvature whichis complementary to a preferred arc of articulation between the adjacentelements.

At least one of said elements (more preferably each element) in the oreach array has a main body with a hardness of at least 7.5 GPa (Hv_(0.5)750 Kg mm⁻²), more preferably a hardness of at least 15 GPa (Hv_(0.5)1500 Kg mm⁻²).

At least one of said elements (more preferably each element) in the oreach array has a main body with an acoustic impedance of at least 25MRayl, more preferably an acoustic impedance of at least 35 MRayl.

In preferred embodiments, at least one of said elements (more preferablyeach element) in the or each array includes a main body and a facingover said main body, such as layer of polymeric or polymer matrixcomposite material, wherein the facing has an acoustic impedance whichis substantially lower than the acoustic impedance of the main body, forproviding bullet-resistance. The facing preferably has an acousticimpedance which is less than the of 25% of the acoustic impedance of themain body.

The main body preferably has an acoustic decoupling facing configured topermit pre-compression of the main body upon impact from a bullet.

The main body preferably has an acoustic decoupling facing configured toreduce the transmission of shock waves to the main body as a result ofimpact from a bullet.

In preferred embodiments, the armour element includes a hard main bodymounted on a base, for example a layer of metal material. The base ispreferably configured to provide lateral constraint for side regions ofthe hard main body.

The amour elements preferably include a main body of ceramic orceramic-ceramic composite or ceramic-metal composite material. Thearmour elements are preferably of the same kind and configuration, andmay be polygonal in plan view (e.g. octagonal).

There is also provided personnel armour to be worn by a userincorporating a flexible armour system in accordance with the aboveaspect of the invention.

Aspects of the invention are particularly, but not exclusively,applicable to body armour, i.e. armour intended to be worn by a human oranimal, or armour which is intended to cover movable plant or machinery,such as gun turrets on military vehicles and craft.

Other aspects and features of the invention will be readily apparentfrom the claims and the following description, which is made by way ofexample only, with reference to the accompanying drawings, in which:

FIG. 1 is a schematic plan view of a section of body armour;

FIG. 2 is schematic view from underneath the body armour section of FIG.1;

FIG. 3 shows an octagon with its sides numbered from one to eight; and

FIG. 4 shows a modified version of the array in FIGS. 1 and 2,consisting of composite armour elements.

Referring firstly to FIGS. 1 and 2, an array of armour elements for usein a flexible armour system is indicated generally at 100.

The array 100 has a first layer consisting of generally octagonalelements 110, which tessellate to form a central aperture (not shown).The octagonal elements 110 are of identical shape and configuration anddefine a generally planar upper surface 112.

A generally square cover element 120 is provided over the centralaperture. The cover element 120 is configured to cover a significantproportion of the joint 130 between adjacent pairs of the tessellatedelements 110 when the upper surfaces 112 of the elements 110 in thefirst layer are in register with one another. In the illustratedembodiment, it can be seen that the cover element is configured to coverapproximately 50 percent of each joint 130.

The joint 130 between adjacent pairs of said elements 110 is configuredto enable articulation between the adjacent elements 110. In thisembodiment, each joint consists of a nested arrangement, wherein aconvex formation on one side of the joint 130 is received in acomplementary concave formation on the other side of the joint 130.Taking the octagon in FIG. 2 as an illustrative example (in which thesides of the octagon are numbered 1 to 8), the corresponding sides 1 and7 on each element 110 are concave and the diametrically opposite sides 3and 5 on each element 110 are convex. This nested arrangement enablesrolling between adjacent pairs of said elements 110 in the array 100.

The degree of articulation between adjacent elements 110 is purposefullyrestricted to prevent or limit the risk of significant gaps from beinggenerated between adjacent elements 110 in the array 100. In thisembodiment, the concave sides of each element 110 incorporate an ear 114having a recess 116, and the convex sides of the element 110 have a ribor projection 118 (see FIG. 2) configured to be received in the recess116 of an adjacent clement 110. The recess 116 acts as a limit stop forthe projection 118, so as to limit the degree of rolling at each joint130.

Each ear 114 is configured to extend beneath an adjacent element in thearray and has a curvature which is complementary to the articulation ofthe adjacent elements.

It is known that bullets containing lead or other filler material maypartially vaporise and melt upon striking armour. The resultant materialmay seep in to or penetrate weak points in the armour, which may injurethe wearer of the armour. This phenomenon is known as bullet splash.However, the elements 110 incorporate deflectors and traps for reducingthe deleterious effects of bullet splash. In this embodiment, the ears114 are arranged such that molten material, upon contact with an ear114, is deflected from its path through at least 45 degrees and morepreferably through 90 degrees, so as to greatly reduce or eliminate thepenetrative force of the molten material. Furthermore, the recesses 116act as a trap for collecting such molten material.

It is preferred if the inter-engaging surfaces between adjacentelements, e.g. the curved and convex formations, are mirror-finishedand/or are coated with a low friction material. The coating may includea lower layer which is hard undercoat, a priming layer over said lowerlayer and a top layer adhered to the priming layer. Preferably, at leastthe top layer has a very low coefficient of friction and is very hard.

The cover element 120 has a cap 122 and a stem (not shown) dependingfrom the cap 122, wherein the cap is of greater diameter than the stem(and is therefore generally mushroom-shaped). In use, the cap 122 isintended to sit over the central aperture between the elements 110. Thecap 122 rests in abutment with the upper surfaces 112 of the elements110, when the stem is received in the central aperture. The cap 122 ispreferably dome-shaped, for deflecting armour piercing bullets.

The cover element 120 is preferably arranged so as to be free-floatingin the array 100, and thereby able to move in response to movement ofone or more of the elements 110 in the array 100. For example, as thearray 100 is flexed in use, the cover element 120 is able to rock on theunderlying elements 110, with the stem moving inwards or outwards withrespect to the central aperture, depending on the direction of flex ofthe array 100.

A plate or back stop 124 is preferably connected to the stem of thecover element 120. The back stop 124 provides additional cover for thecentral aperture between the elements 110 and also acts as a splashtrap. Moreover, it provides support for the back face of array 100.

The stem of the cover element 120 acts as a spacer between the cap 122and back stop 124, and is configured to ensure that the cap 122 staysclose to or in abutment with the octagon elements 110 when the array 100is flexed.

An additional backing layer may be provided behind the array 100, e.g.for collecting spall or sporation from the armour elements 110.

Whereas, typically, the array 100 may be worn as armour over a ballisticvest, the use of a sporation collecting layer behind the array 100renders such undergarments unnecessary. In one embodiment, the backinglayer consists of an array of overlapping elements provided on the backstops 124. These elements will preferably have a much greater surfacearea than the back stops 124, in order to overlap with one another andthereby provide a substantially continuous layer behind the array 100.These elements may be adhered or otherwise affixed on the back stops124, and preferably comprise a hard fibrous composite armour material.

The elements 110 in the array 100 are preferably coupled together usinga tape or other material in such a way as to pre-tension the array 100.The material preferably has predetermined stretch and overstretch limitsand may be applied to front and/or back faces of the array 100. Thepre-tensioning material may be mechanically affixed and/or bonded to theelements 110 in the array 100.

The armour elements 110 may take various forms and may have a solid orcomposite structure. Each element 110 consists of a main body of hardmaterial, and in the most preferred embodiments, the elements 110 have ahardness in the region of 15 GPa (Hv_(0.5) 1500 Kg mm⁻²) and an acousticimpedance in the region of 35 MRayl.

The main body is preferably is mounted on a base member. Morepreferably, the main body is at least partially contained on a basemember. Such an arrangement is illustrated in FIG. 4, wherein eachelement 110 has a main body 140, which is partially contained incup-type backing or base 142. The base 142 is preferably of high tensilestrength material, such as titanium, steel, aluminium. Alternativematerials include polymer matrix composites based on glass fibre,carbon, aramid, polyethylene or similar fibres with an extremely hightensile modulus, or alternatively a high strength plastic such aspolycarbonate or nylon.

The base 142 is preferably configured to constrain outward movement ofthe hard material in the event of a ballistic strike. This is ofparticular advantage if the hard main body 140 is brittle in character,e.g. if made of a ceramic material.

It is preferred if the main body 140 of the element is located on itsbase 142 in such a way as to protect the hard element from shock waveswhich may be reflected by the base member 142 in the event of aballistic strike. This may be achieved by using a rubbery polymer toaffix the hard element 140 on the base 142, thereby localising shockwaves from any impact to the hard element 140. Alternatively, the mainbody 140 may be partially coupled or acoustically matched to the basemember 142. This can be achieved by cementing the hard element 140 tothe base 142 using a material having an acoustic impedance greater than10 MRayl, e.g. a soft metal such as brass, or a braise, or an inorganiccement, or a high density metal powder such as tungsten with a polymericmatrix. Alternatively, the base 142 may be moulded or formed around themain body 142 at the time of manufacture. The coefficient of thermalexpansion of the base material (e.g. a metal) is preferably higher thanthe main body material (e.g. a ceramic or metal/ceramic composite),thereby ensuring a shrink fit of the base 142 on the main body 140,promoting good acoustic coupling. These coupling arrangements are usefulin dispersing the energy throughout the system and thus delaying thefracture of the hard element 140 and the joint between the elements 110.

The main body 140 preferably has a facing 144, e.g. of polymericmaterial, which is configured to enable pre-compression of at least anupper region of the hard main body, upon impact from a bullet or thelike. It is particularly preferred if the facing 144 acts as an acousticdecoupling layer between a hard cored ballistic strike and the hard mainbody 140 of the element 110, for preventing or reducing the transmissionof sound waves through to the hard element 140.

An armour system incorporating a plurality of such elements 110 in anarray may include a continuous facing layer arranged to cover at leastone of the elements in the array, as opposed to individual facings 144for each element.

The facing 144 is further advantageous in that any sporation that isdeveloped after the hard element 140 has started to fail during aballistic strike is channelled out in the direction of the bullet. Thishas the effect that a significant proportion of the kinetic energy ofthe bullet is channelled back in the direction of the bullet, thusmitigating the effect of the impact. The high impedance of the hardmaterial simultaneously produces a shockwave in the bullet coresufficient to fragment it, thus dispersing the kinetic energy of thebullet.

In preferred embodiments the hard elements in the array 100 will be ofceramic or ceramic-composite structure, e.g. from alumina and aluminiumoxide and composites thereof. However, other hard materials may be used,such as borides (e.g. titanium diboride), carbides (e.g. boron andsilicon carbide), nitrides (e.g. silicon nitride) and metal-matrixcomposites such as carbides and borides in a metal matrix, orceramic-matrix composites which are mixtures of hard engineeringceramics. However, for lower level armour threats, softer materials suchas glass or silicate ceramics may be used.

Although the above description and statements of invention refer tooctagonal armour elements, the armour elements may have an alternativepolygonal configuration capable of a tessellation in an array whichdefines an aperture between the adjacent elements in the array, e.g. agenerally regular polygon having in excess of eight sides.

1. A flexible combat armour system including a group of bullet-resistantarmour elements arranged in a tessellated array, wherein each armourelement in said group includes a hard main body mounted on a base,wherein the base is configured to provide lateral constraint for sideregions of the hard main body, and wherein the main body is of ceramicor ceramic-ceramic composite or ceramic-metal composite material,further wherein the main body exhibits one or more of: a hardness of atleast 7.5 GPa (Hv_(0.5) 750 Kg mm⁻²), for providing bullet-resistance, ahardness of at least 15 GPa (Hv_(0.5) 1500 Kg mm⁻²), for providingbullet-resistance, an acoustic impedance of at least 25 MRayl, forproviding bullet-resistance, an acoustic impedance of at least 35 MRayl,for providing bullet-resistance; further wherein each of said elementsis movable relative to an adjacent element in the array, and a nestedjoint is provided between the adjacent elements, such that an armourelements nests with each adjacent element, and the nested joint isconfigured to permit rolling articulation between said elements, andfurther wherein the array defines an aperture between the group ofarmour elements, and a cover element is arranged to cover the apertureand a significant portion of the joint between the adjacent pairs of thetessellated elements when the upper surfaces of the elements are inregister with one another, wherein the cover element is movable relativeto each of said tessellated armour elements, and has a stem whichextends through the aperture between the tessellated armour elements,and a back stop is connected to the stem to limit movement of the coverelement relative to the array.
 2. The An armour system according toclaim 1, including a plurality of said groups, each group having its owncover element.
 3. (canceled)
 4. The armour system according to claim 2wherein the back stop includes a backing element, and respective backingelements in the system are configured to overlap with one another so asto form a backing layer suitable for collecting sporation or debrisbehind the array of armour elements.
 5. The armour system according toclaim 4 wherein the backing elements comprise a hard fibrous compositearmour material.
 6. (canceled)
 7. The armour system according to claim 1wherein the cover element is configured to cover approximately 50percent of each joint.
 8. (canceled)
 9. The armour system according toclaim 1 wherein the cover element has a cap which rests in abutment withthe upper surfaces of the elements in the array.
 10. The armour systemaccording to claim 9 wherein the cap is dome-shaped, for deflectingarmour piercing bullets.
 11. (canceled)
 12. (canceled)
 13. The armoursystem according to claim 1 including limit stops between adjacentelements in the array, to restrict the degree of articulation betweenthe adjacent elements.
 14. The armour system according to claim 1wherein the nested joint is defined by a convex formation on one elementand a complementary concave formation on the other element.
 15. Thearmour system according to claim 1, wherein adjacent elements in thearray are arranged for articulation relative to one another, and whereinthe degree of articulation between the adjacent elements is restrictedto prevent or limit the risk of significant gaps from being generatedbetween the adjacent elements.
 16. The armour system according to claim15 wherein a rolling joint is provided between the adjacent elements inthe array, consisting of a concave side on one of the elements which isnested with a convex side on the other of said elements, and wherein theconcave side incorporates an ear having a recess, and the convex sidehas a rib or projection configured to be received in the recess of anadjacent element, wherein the recess acts as a limit stop for theprojection, so as to limit the degree of rolling at each joint.
 17. Thearmour system according to claim 16 wherein the ear acts as a deflectorfor deflecting bullet splash, and the recess acts as a trap forcollecting bullet splash.
 18. (canceled)
 19. The armour system accordingto claim 16 wherein the ear is configured to extend beneath an adjacentelement in the array.
 20. The armour element according to claim 17wherein the ear has a curvature which is complementary to an arc ofarticulation between the adjacent elements.
 21. (canceled) 22.(canceled)
 23. (canceled)
 24. (canceled)
 25. (canceled)
 26. (canceled)27. (canceled)
 28. (canceled)
 29. The armour system according to claim16 wherein each armour element in the group includes a projection whichis configured to be received in the recess of an ear on an adjacentelement in the array, wherein the recess and projection cooperate tolimit articulation between the two elements.
 30. (canceled) 31.(canceled)
 32. (canceled)
 33. (canceled)
 34. The armour system accordingto claim 1 wherein at least one of said elements includes a facing oversaid main body, wherein the facing has an acoustic impedance which issubstantially lower than the acoustic impedance of the main body, forproviding bullet-resistance.
 35. (canceled)
 36. The armour systemaccording to claim 34 wherein the main body has an acoustic decouplingfacing configured to permit pre-compression of the main body upon impactfrom a bullet.
 37. (canceled)
 38. (canceled)
 39. (canceled) 40.(canceled)
 41. (canceled)
 42. (canceled)
 43. The armour system accordingto claim 1 wherein the elements are octagonal in plan view. 44.Personnel armour to be worn by a user, the personnel armourincorporating a flexible armour system in accordance with claim 1.45.-60. (canceled)